I've been outlining some ideas for a post Nemesis Star Trek series set in the early 25th century. Say around 2410-15 give or take. I've wondered what would be the oldest starship classes that would be in service for Starfleet in that era? While the Excelsior and Miranda class ships served in abundance in the Dominion War they seem pretty dated and took very heavy losses in combat so I'm figuring that they would be retired en masse after the war was over. The Constellation class while it popped up a couple of times in regular Starfleet service during TNG (Gettysburg and one of the ships in Redemption II) it looks even more dated than the Miranda's. I'm betting the oldest ships would be the Ambassador class and its variants and also possibly the on occasionally glimpsed New Orleans class which seemed to be from that general time period.